The present invention relates to a method of checking cigarettes.
The present invention may be used to advantage on the input unit of a cigarette packing machine, to which the following description refers purely by way of example.
Known packing machines normally comprise an input unit featuring an input hopper, the outlet of which is defined by a number of side by side channels for successively feeding superimposed, parallel, horizontal layers of cigarettes to an extracting device moving back and forth through the outlet of the hopper to feed the layers to a device for forming groups of cigarettes.
On some known packing machines, the cigarettes are not checked until after the groups are formed, and any groups comprising even only one faulty cigarette are rejected.
To save economically on the number of cigarettes rejected, U.S. Pat. No. 4,592,470, for example, proposes checking the cigarettes inside the hopper, and rejecting any faulty cigarettes before the groups are formed.
The above method, however, involves several drawbacks, mainly on account of the cigarettes not always being arrested in the same position in front of the checking device. That is, as the cigarettes must be checked and possibly rejected before reaching the extracting device, the checking and extracting devices must be located a given distance apart, so that a column of cigarettes is formed between the two devices, and which varies in height according to humidity, any minor differences in diameter, and the traveling speed of the cigarettes (the faster the cigarettes travel, the more the cigarettes in the column are compressed when arrested). As a result, the cigarettes are not always arrested in the same position in front of the checking device, thus resulting in possible reading errors, and in full cigarettes being rejected or, worse still, partly empty cigarettes being passed.